Radiation Protection Course Equipment Specs

Radiation Protection Course For Radiologists
Lecture 8 of 8
Procedures for Minimizing Dose to Patients
And X-ray Personnel
Prof Amin E AAmin
Dean of the Higher Institute of Optics Technology
&
Prof of Medical Physics
Radiation Oncology Department
Faculty of Medicine, Ain Shams University

New X-Ray Equipment
• All new medical x-ray equipment and accessories for such
equipment, must conform to the requirements of the Egyptian
law and regulations of installing new radiology equipment.
• These regulations specify standards of design, construction
and performance, with respect to radiation safety, and are
mandatory requirements for new equipment only.
• It is the responsibility of the manufacturer or distributor to
ensure that the equipment conforms to the requirements of
the regulations.

Warning Signs
• The x-ray control panel must bear a permanent and conspicuous
sign warning that hazardous x-radiation is emitted when the
equipment is in operation and prohibiting unauthorized use.

Markings
• All controls, meters, lights and other indicators relevant to the
operation of the equipment must be readily discernible and
clearly labeled or marked as to function.

Indicator Lights
• There must be readily discernible, separate indicators on the
control panel that respectively indicate:
(i) when the control panel is energized and the machine is ready to
produce x-rays, and
(ii) when x-rays are produced.
(iii)When more than one x-ray tube is controlled by one control panel,
there must be clear and visible indication, at or near the tube housing
and on the control panel, of which tube is connected and ready to be
energized.

Focal Spot
• The location of the focal spot must be clearly and accurately
marked on the tube housing.

Filtration
• The external surface of the x-ray tube housing must bear a
permanent mark or label which sets out the minimum
permanent inherent filtration in the useful beam, expressed as
millimetres of aluminum equivalent at a specified peak tube
potential.

Filtration
• The total permanent filtration in the useful beam must be
equivalent to at least the following thicknesses of aluminum:
(i) 0.5 millimetre of aluminum, for machines designed to operate with
x-ray tube potentials below 50 kilovolts peak;
(ii) 1.5 millimetres of aluminum, for machines designed to operate
with x-ray tube potentials from 50 kilovolts peak to 70 kilovolts
peak, and
(iii) 2.5 millimetres of aluminum, for machines designed to operate
with x-ray tube potentials above 70 kilovolts peak;

Mechanical Stability
• The x-ray tube must be securely fixed and correctly aligned
within the tube housing.
• Also, the tube housing must maintain its required exposure
position or movement without excessive drift or vibration
during operation.
• The x-ray tube housing must be supported by mechanical
means. It must not be hand-held during operation.

Exposure Control
• There must be an exposure switch, timer, or other device to
initiate and terminate x-ray production.
• This control must automatically terminate the exposure after a
preset time, product of current and time, or exposure has
elapsed.

Exposure Control
• The exposure switch must:
(i) require continuous pressure by the operator to produce x-rays (i.e.,
“dead man” type);
(ii) if in the form of a footswitch, be so constructed that if overturned
inadvertent exposures do not result;
(iii) be so located that convenient operation outside of a shielded area is
not possible, (except for exposure switches used in conjunction with
mobile x-ray equipment, with spot film devices, in fluoroscopy and with
certain special procedures), and
(iv) for mobile x-ray equipment, be equipped with a cable at least three
meters long.

Indication of Technique Factors
• The actual peak kilovoltage should correspond to the selected
or indicated value to within 5% of the selected or indicated
value.
• The millammeter should be accurate to within 5% of the full
scale reading and be temperature compensated for normal
operating conditions.

X-Ray Tube Shielding
• The shielding of the housing must be such that, at each rating
specified by the manufacturer for that tube, the leakage
radiation, measured at a distance of one metre in any direction
from the focal spot of the x-ray tube, does not exceed 0.1% of
the exposure rate at the same distance along the central axis of
the useful beam.

Stationary General Purpose
Radiographic Equipment

Collimation
• The x-ray tube housing must be equipped with an adjustable
collimator which provides stepless adjustment of the size of
the x-ray field and which must provide the same degree of
shielding towards leakage radiation as is required of the tube
housing.
• The collimator should incorporate means to indicate the size
of the x-ray field at the image receptor. if in the form of a
light localizer, it should give an average illumination of at
least 100 lux at 100 cm or the maximum target-to-image
receptor distance, whichever is less.

Filtration
• The filters must be permanently and securely mounted to the x-
ray port of the tube housing or beam limiting device, or both.

Timer Accuracy
• The timer or exposure control must be such that:
(i) it can be set to control exposures as short as 1/60 second or 5
milliampere-seconds, whichever is greater, and
(ii) at each setting it is accurate to 1/60 second or 7% of that setting,
whichever is greater.

Reproducibility
• The coefficient of variation of any 10 consecutive radiation
measurements, taken at the same source-to-detector distance
within a time period of one hour and with the line voltage for
each measurement within 1% of the mean value for all of the
measurements, must not be greater than 0.05.
• Furthermore, each of the 10 radiation exposures measured
must be within 15% of the mean value of the 10
measurements.

Linearity
• For any fixed value of x-ray tube potential (in kVp), within
the range of values specified for the equipment, the average
ratios of exposure (in milliroentgen or coulomb/kg) to tube
current-exposure time product (in milliampere-seconds) at
any two consecutive tube current settings must not differ by
more than 0.10 times their sum.

Line Voltage Compensator
• The equipment must be equipped with means to compensate for
variations in x-ray tube potential caused by line voltage
fluctuations.
• By these means it must be possible to set and maintain the peak
tube potential (kVp), prior to initiation of an exposure, to within
5% of the selected value, for a line voltage variation of ± 7% of
its nominal value.

Current Stabilization
• The equipment should be provided with a tube current stabilizer
to maintain preset current to within ± 5% of the required value
for exposures of 1/5 second or more.
• Changes in tube potential should not result in a variation of tube
current greater than ± 5%.

Mobile Radiographic Equipment
• The requirements given above should be, applied.
• Additional requirements for mobile radiographic equipment are
as follows:

Target-To-Skin Distance
• The equipment must be equipped with means to prevent
operation at target-to-skin distances of less than 30 centimetres.

Exposure Control
• The exposure switch must be of the deadman type and must be
provided with a cable at least 3 metres long.

Capacitor Discharge Equipment
Capacitor discharge type mobile equipment must be equipped with:
– a safety shutter or other means to prevent emission of xradiation from
the exit port of the x-ray tube housing assembly when the exposure
switch or timer is not activated;
– a warning light, or other visual indicator, to indicate that the high
potential capacitor is charged;
– an electrical meter, or other indicator, to indicate the state of charge of
the high potential capacitor, and
– means to enable the high potential capacitor to be discharged to a
residual potential difference of less than 30 volts, without the production
of x-radiation.

Collimation
• The x-ray tube housing must be equipped with an adjustable
collimator and which must provide the same degree of
shielding towards leakage radiation as is required of the
tube housing.
• The maximum size of x-ray field permitted by the
collimator should not be larger than the useful area of the
input phosphor on the image intensifier. The useful beam
should be centred on the input phosphor and the beam
margins should be tangential to the area being viewed.

Direct Bean Absorbers
• A primary protective barrier must be permanently incorporated
into the equipment to intercept the entire cross section of the
direct beam, for all possible target-to image receptor distances.
The barrier must be so installed that its removal from the
useful beam causes automatic termination of the exposure
• The lead equivalent thickness of the primary protective barrier
must be at least 2 mm for machines capable of operating up to
100 kVp. For each additional kilovolt of operating tube
potential an additional 0.01 mm lead equivalent is required.

Direct Bean Absorbers
• A primary protective barrier must be permanently incorporated
into the equipment to intercept the entire cross section of the
direct beam, for all possible target-to image receptor distances.
• The barrier must be so installed that its removal from the useful
beam causes automatic termination of the exposure

Image Intensification
• All fluoroscopic x-ray machines must be equipped with an
image intensification system.
• The image intensification system must be adequately shielded
so that neither the useful beam nor the scattered radiation from
the intensifier will produce significant exposure to the operator
or other personnel.

Image Intensification
• The image intensification system must be adequately shielded so
that neither the useful beam nor the scattered radiation from the
intensifier will produce significant exposure to the operator or
other personnel.
• The shielding must be such that the exposure rate to an object
having a cross-sectional area of 100 cm2, with no linear dimension
greater than 20 cm, of x-radiation due to transmission of the useful
beam through or scattering from the window of the fluoroscopic
imaging assembly, does not exceed 2 milliroentgen per hour (516
nC/kg/h) at 10 centimetres behind the plane of the image receptor,
for each roentgen per minute of entrance exposure rate.

Target-To-Skin Distance
• Fixed fluoroscopic equipment must incorporate means to
limit the target-to-skin distance to not less than 38 cm.
• In the case of a fluoroscopic machine designed for
special applications that would be impossible at the
above minimum distance, provision may be made for
operation at shorter target-to-skin distances; but in no
case must this distance be less than 20 cm.

Material Between Patient And
Image Receptor
• The aluminum equivalent of the table top must not be greater
than 1 mm when measured at 100 kVp.

Exposure Switch
• The fluoroscopic exposure switch must be of a dead-man type.

Timer
• There must be a cumulative timing device, activated by the
fluoroscopic exposure switch, which requires manual resetting.
• This timer must have a maximum setting not exceeding 5
minutes. Whenever a preset time has been reached, it must give
a clearly audible signal.

Indication of Tube Potential and Current
• Electrical meters or other visual indicators must be provided to
enable continuous monitoring by the operator of tube potential
and current during fluoroscopy.

Entrance Exposure Rate
• At the shortest target-to-skin distance specified for the
equipment, the entrance exposure rate must not exceed 10
roentgen (2.58 mC/kg) per minute for any combination of tube
current and potential. With modern equipment most
fluoroscopy can and should be carried out with exposure rates
of less than 5 roentgen (1.29 mC/kg) per minute.

Bucky Slot Shielding
• Shielding must be provided with the equipment to cover the
Bucky Slot. This should provide the equivalent protection of at
least 0.5 mm of lead at 100 kVp.

Table Shielding
• The side of the fluoroscopic table should have an equivalent
thickness of at least 0.5 mm of lead at 100 kVp to restrict
scattered radiation passing through it.

Operator Shielding
• To protect the operator from radiation scattered above the
table-top, there should be a lead rubber apron of
dimensions not less than 45.7 cm × 45.7 cm (18" × 18").
• The material must have a lead equivalent of not less than
0.5 mm at 100 kVp and the apron must be attached to the
lower edge of the fluoroscopic screen when the latter is
vertical and to the side when the screen is horizontal.
• The apron may consist of several overlapping parts.

Operator Shielding
• In the absence of such a protective apron a retractable lead
shield must be Incorporated in the equipment to project at
least 15 cm above the table when in use.
• It must be mounted on the front side of the table and have a
lead-equivalent thickness of at least 0.5 mm at 100 kVp.

Collimation
• The equipment must be permanently fitted with a
collimator which must confine the beam to the area of the
fluorescent screen.
• The beam must not be greater than 35 cm × 43 cm (14" ×
17") at the screen surface, regardless of the target-to-skin
distance.

Beam Alignment
• The photofluorographic camera and x-ray tube must be coupled
together so that the direct beam always centres on the mid-point
of the screen.

Gonad Shield
• The lower edge of the beam-defining device should be curved
to prevent irradiation of the female gonads.

Maximum Entrance Exposure
• The entrance exposure to a patient must not exceed 200
milliroentgen and should not exceed 100 milliroentgen (25.8
microcoulomb/kg) per film.

Protective Clothing
1. Protective body aprons
2. Gonad shields
3. Protective gloves

Protective Body Aprons
• Protective body aprons used for radiographic or fluoroscopic
examinations with peak x-ray tube potentials of up to 150 kVp
must provide attenuation equivalent to at least 0.5 mm of lead.

Gonad Shields
• Contact-type gonad shields used for routine diagnostic
radiology must have a lead equivalent thickness of at least 0.25
mm and should have a lead equivalent thickness of 0.5 mm at
150 kVp.
• Contact-type gonad shields must be of sufficient size and shape
to exclude the gonads completely from primary beam
irradiation.

Protective Gloves
• Protective gloves used in fluoroscopy must provide attenuation
equivalent to at least 0.25 mm of lead at 150 kVp.

Film Cassettes
• The front panel of the film cassette must not exceed an
aluminum equivalence thickness of 1.0 mm and should not
exceed an aluminum equivalence thickness of 0.5 mm.
• Film cassettes must be completely light-tight. As soon as
the material used for achieving light-tightness becomes
worn and light leakage occurs, either the material or the
cassette should be replaced.
• It is also important to have good film-screen contact;
therefore screens should be cleaned regularly and their
contact with the film checked.

Procedures To Reduce Dose To
X-ray Personnel

Basic Principles of Dose
Reduction
•Time
•Distance
•Shielding

Reduction of External Dose
❖Minimize the time spent near the radiation source
❖Maximize the distance away from the source
❖Make use of available shielding

General Recommendations
1. Only One Investigation
• An x-ray room must not be used for more than one
radiological investigation simultaneously.
2. Only Essential Persons
• Except for those persons whose presence is
essential, no person must be in the x-ray room
when the exposure is carried out.

3. Be Away from the useful beam
– Personnel must at all times keep as far away from the useful
beam as is practicable. Exposure of personnel to the useful
beam must never be allowed unless the beam is adequately
attenuated by the patient and by protective clothing or screens.

4. Use Protective Devices
– All personnel must take full advantage of the protective devices
available.
5. Stay Behind Shielding
4. Operators should remain inside the control booth or behind
protective screens when making an x-ray exposure. In cases
where there are reasons that make this impractical, protective
clothing must be worn.

6. Rules for patient support
– When there is a need to support children or weak patients,
holding devices should be used.
– If parents, escorts or other personnel are called to assist, they
must be provided with protective aprons and gloves, and be
positioned so as to avoid the useful beam.
– No one person should regularly perform these duties.

7. Personal Dosimetry
– When a lead equivalent protective apron is worn, the personnel
dosimeter must be worn under the apron.
– If extremities are likely to be exposed to significantly higher
doses, additional extremity monitors should be worn.

8. Personal Dosimetry
– All operators of x-ray equipment, together with personnel (e.g.
nurses) who routinely participate in radiological procedures,
and others likely to receive a radiation dose in excess of 1/20th
of the Dose limit specified in Appendix I, must wear personnel
dosimeters.

9. Close All Doors
– All entrance doors to an x-ray room, including patient cubicle
and preparation room doors, should be kept closed while a
patient is in the room.
10.Attend The energized machine
– X-ray machines which are energized and ready to produce
radiation must not be left unattended.

11.In the case of high exposure
– Where radiation doses in excess of 5% of the dose limit specified
in Appendix I are being received regularly by any one person,
appropriate remedial steps must be taken to improve techniques
and protective measures.

12.Machine Operator
– X-ray equipment must only be operated by, or under the
direct supervision of, qualified individuals.
13.Don’t hold the x-ray housing
– An x-ray housing must not be held by hand during
operation.

Recommendations For Operation
Of Radiographic Units
1. Controlling the machines
– The x-ray exposure should, as a general rule, be controlled
from the control panel located inside the control booth or
behind a shielded wall. In the case of special techniques
where the operator is required to control the exposure while
at the side of the patient, appropriate protective clothing
must be worn.

Of Radiographic Units
2. Communication with patient
– The operator must have a clear view of the patient during every
exposure and be able to communicate with the patient and/or
attendants without leaving the control booth.
3. Don’t hold the Cassettes
2. Cassettes must never be held by hand during an exposure.

Recommendations For Operation Of
Fluoroscopic Units
1. Protective Clothing
– All persons, with the possible exception of the patient, required to be
in the room during a fluoroscopic procedure should wear protective
aprons. Lead shields or curtains mounted on the fluoroscopic unit
must not be considered a sufficient substitute for the wearing of
protective clothing.

Fluoroscopic Units
2. Protective Gauntlets
– Protective gauntlets should be worn
by the radiologist during palpation in
every fluoroscopic examination.
During fluoroscopy, palpation with
the hand should be kept to a
minimum.

Of Fluoroscopic Units
3. Protective Clothing
– During fluoroscopy and spotfilm
operation associated with
fluoroscopic operation, where
personnel are required to be at
the side of the patient,
appropriate protective clothing
must be worn by these personnel.

Fluoroscopic Units
4. Shorten The Time
– All fluoroscopic examinations should be carried out as
rapidly as possible and with minimum dose-rates and x-ray
field sizes.
5. Image Intensified Fluoroscopy
– Direct-viewing fluoroscopy must not be carried out; image
intensified fluoroscopy must be used.

Of Mobile Units
1. Don’t Use Mobile If You Can Use Stationary
– Mobile units must be used only if the condition of the
patient is such as to make it inadvisable for the examination
to be carried out with a stationary unit in the main x-ray
department.

Of Mobile Units
2. Don’t Irradiate Other Persons
– During operation, the primary beam should be directed from
occupied areas if at all possible, and every effort must be made
to ensure that this beam does not irradiate any other persons in
the vicinity of the patient.

Of Mobile Units
3. Keep The Distance
– The operator must stand at least 3 metres from the x-ray tube and out of the
direct beam.
4. Use The Shielding
– The operator must be shielded when exposures are made.

Of Mobile Units
5. Discharge The Capacitor
– In a capacitor discharge unit after an x-ray exposure has been
made there is a residual charge left in the capacitors. This
residual charge can give rise to a “dark current” and result in
x-ray emission even though the exposure switch is not
activated. Therefore, the residual charge must be fully
discharged before the unit is left unattended.

Photofluorographic Units
• Photofluorographic x-ray machines in general can give
significantly higher patient doses than conventional diagnostic
machines.

Of Photofluorographic Units
1. Only the operator and the patient should be in the room or
vehicle in which the unit is installed when an exposure is
made.
2. When a photofluorographic unit is mounted in a vehicle
appropriate steps must be taken to ensure that persons awaiting
examination and personnel are protected from exposure to x-
radiation. Such persons should be kept well clear of the vehicle
when exposures are being made.

Recommendations For Special
Radiological Procedures
• Cystoscopic radiography
• Hystero-salpingography
• Needle Biopsies of the Lung
• Transhepatic Needle Cholangiography
• Pancreatography, and other similar procedures.

• In these procedures the radiologist and other personnel in the
vicinity of the patient can be subjected to appreciable scattered
radiation from the patient when the x-ray beam is on.
Therefore, the radiologist and other personnel should wear
protective glasses and clothing and should remain as far away
from the patient as practicable, unless adequate scatter shields
can be incorporated into the x-ray equipment.

• The protective devices (e.g., shielded panels, leaded drapes,
extended collimator cones, etc.) provided with the x-ray
equipment should be used whenever they do not interfere
unduly with the diagnostic procedures.
• The smallest x-ray field consistent with the procedure should
be used.

• Angiography. Angiography is potentially one of the sources of
greatest exposure to personnel in diagnostic radiology, since it
requires the presence of a considerable number of personnel
close to the patient and involves fluoroscopy for extended
periods of time and multiple radiographic exposures. For such
procedures all personnel must be aware of the radiation hazards
involved and make every effort to adhere to the
recommendations below:

1. Use Fully protected Device
– Full use must be made of the protective devices provided with x-
ray equipment (e.g., shielded panels, leaded drapes, bucky slot
covers, etc.).
2. Wear Protective Clothing
– All personnel must wear protective clothing and personnel
dosimeters. Protective glasses should also be worn.

3. Go Away or behind shield
– All personnel who are not required to be immediately adjacent to the
patient during the procedure must stand back as far as possible from
the patient and, if at all possible, should stand behind a protective
shield.
4. Use shields if possible
– Where indicated and feasible, special shields in addition to the
protective devices provided with the machine should be used.

Procedures For Minimizing Dose To
Patients

Guidelines For The Prescription Of
Diagnostic X-ray Examinations
• The medical practitioner is in a unique position to reduce
unnecessary radiation exposure to the patient by ensuring that
all examinations are clinically justified. The practitioner can
achieve this by adhering, as much as possible, to certain basic
recommendations. These are as follows:

Guidelines For The Prescription
Of Diagnostic X-ray Examinations
1. The prescription of an x-ray examination of a patient should
only be based on a clinical evaluation of the patient and
should be for the purpose of obtaining diagnostic information.
2. Routine or screening examinations, such as for
preemployment physical examinations, tuberculosis
screening, mass mammographic screening, etc., in which
there is no prior clinical evaluation of the patient, should not
be prescribed.

3. It should be determined whether there have been any previous
x-ray examinations which would make further examination
unnecessary, or allow for the ordering of an abbreviated
examination. Relevant previous radiographs or reports should
be examined along with a clinical evaluation of the patient.
4. When a patient is transferred from one physician or hospital
to another any relevant radiographs or reports should
accompany the patient and should be reviewed by the
consulting physician.

5. When prescribing a radiological examination, the physician
should specify precisely the clinical indications and
information required.
6. The number of radiographic views, required in an
examination, should be kept to the minimum practicable,
consistent with the clinical objectives of the examination.
7. In prescribing x-ray examinations of pregnant or possibly
pregnant women, full consideration should be taken of the
consequences of foetal exposure.

8. If a radiograph contains the required information, repeat
exposures should not be prescribed simply because the
radiograph may not be of the “best” diagnostic quality.
9. Specialized studies should be undertaken only by, or in
close collaboration with, a qualified radiologist. Medical
practitioners should not operate x-ray equipment, or be
responsible for the use of such equipment.

10.A patient’s clinical records should include details of x-ray
examinations carried out.
11.The prescription of an x-ray examination of a patient should
only be based on a clinical evaluation of the patient and should
be for the purpose of obtaining diagnostic information.
12.Routine or screening examinations, such as for
preemployment physical examinations, tuberculosis screening,
mass mammographic screening, etc., in which there is no prior
clinical evaluation of the patient, should not be prescribed.

13.It should be determined whether there have been any previous
x-ray examinations which would make further examination
unnecessary, or allow for the ordering of an abbreviated
examination. Relevant previous radiographs or reports should
be examined along with a clinical evaluation of the patient.
14.When a patient is transferred from one physician or hospital to
another any relevant radiographs or reports should accompany
the patient and should be reviewed by the consulting physician.

15.When prescribing a radiological examination, the physician
should specify precisely the clinical indications and
information required.
16.The number of radiographic views, required in an examination,
should be kept to the minimum practicable, consistent with the
clinical objectives of the examination.
17.In prescribing x-ray examinations of pregnant or possibly
pregnant women, full consideration should be taken of the
consequences of foetal exposure.

18.If a radiograph contains the required information, repeat
exposures should not be prescribed simply because the
radiograph may not be of the “best” diagnostic quality.
19.Specialized studies should be undertaken only by, or in close
collaboration with, a qualified radiologist. Medical
practitioners should not operate x-ray equipment, or be
responsible for the use of such equipment.
20.A patient’s clinical records should include details of x-ray
examinations carried out.

Guidelines For Radiography Of
Pregnant Women
• Every effort should be made to avoid unnecessary irradiation of
any woman known to be, or who might be pregnant. This is
particularly important during the earliest stages of pregnancy
when the potential for radiation damage of the rapidly dividing
tissues is the greatest. Clearly, however, in spite of the
possibility of radiation damage, if a radiological examination is
required for the diagnosis or management of an urgent medical
problem it must be done, irrespective of whether the patient
may or may not be pregnant.

Pregnant Women
• The following recommendations apply to x-ray
examinations involving pregnant or potentially
pregnant women:

Pregnant Women
1. Ten day Role
– Radiography of the pelvic area in women of child-bearing age
should be undertaken in the ten-day period following the
onset of menstruation, since the risk of pregnancy is very
small during this period.

Pregnant Women
2. No Elective Abdominal nor Pelvic X-ray
– Only essential investigations should be taken in the case of
pregnant or suspected pregnant women. Elective radiography
of the abdominal and pelvic area in pregnant women must be
avoided. (“Elective” is taken to mean an examination of the
abdomen and pelvis which does not contribute to the diagnosis
or treatment of a women in relation to her immediate illness.)

Pregnant Women
3. No Photofluorographic
– Pregnant women or women who may be pregnant must
not be accepted for chest photofluorographic (mass
radiographic) examinations.

Pregnant Women
4. Use protective Shields
– When radiography of the pelvic area
or abdomen is required, the exposure
must be kept to the absolute
minimum necessary and full use
must be made of gonadal shielding
and other protective shielding if the
clinical objectives of the
exmaination will not be
compromised.

Pregnant Women
5. Foetal dose is lower in prone Position
– If a radiographic examination of the foetus is required the prone
position should be used. This has the effect of shielding the
foetus from the softer x-rays and hence reducing the foetal dose.

Pregnant Women
6. Radiography should not be used for the determination of
abnormal presentations of the foetus, or for placenta
localizations. Other techniques such as ultrasonography
are better suited for this purpose.

Pregnant Women
7. Use Well-Collimated X-Ray Beam
– Radiography of the chest, extremities, etc., of a pregnant woman,
for valid clinical reasons, should only be carried out using a well-
collimated x-ray beam and with proper regard for shielding of the
abdominal area.

Guidelines For Radiographic Examination
Of The Breast (Mammography)
The recommendations that follow are intended to provide
guidance to the technologist, the medical physicist and
radiologist in exercising their responsibility towards reduction
of patient dose.
1. The mammographic X-ray system must be designed
specifically for mammography and the image receptor must
be compatible with the system.
2. A film-screen combination that provides good quality
diagnostic results must be used. Direct exposure film must
never be used in mammography.

3. Except in the case of mammography performed within a
screening program, the technologist must not perform any
examination which has not been prescribed by a physician
responsible for the patient.
4. The dose to the patient must be kept to the lowest practicable
value consistent with clinical objectives, and without loss of
essential diagnostic information. To achieve this, techniques
appropriate to the equipment available should be used and
evaluated from time to time in terms of effectiveness.

5. Particular care in patient X-ray protection must be taken when
mammographic X-ray examinations of pregnant or possibly
pregnant women are carried out, even though the radiation dose to
the abdomen and fetus are negligible during normal mammographic
X-ray examinations.
6. There may be a need to use special procedures when performing
mammographic X-ray examinations of patients with breast implants
such as extra views, modified positioning, compression and loading
techniques. Particular care of compression techniques must be taken
since excessive compression of the implants during mammographic
X-ray examination may cause rupture of the implant.

7. In mammography, it is recommended that the field normally be
the full size of the image receptor, but not larger than the image
receptor support, except at the chest wall. The amount of
unexposed areas on the films should be minimal so to avoid the
need for masking. Collimated-down views are useful in some
purposes, but should be considered as a special procedure.
8. Appropriate compression must be used in all mammographic
procedures.
9. Adequate X-ray beam filtration must be used in all
mammographic procedures.

10.The technologist should use the maximum focal spot to skin
distance consistent with good radiographic loading. For
mammographic procedures, distances of less than 50 cm
should not be used. For mammographic procedures including
magnification, distances of less than 25 cm to the entrance
surface of the breast shall not be used.
11.Full details of the mammographic procedures, including
retakes, carried out should be noted on the patient’s clinical
records.

12.Irradiation times should be minimized to avoid unnecessary dose
increase from reciprocity law failure and to avoid motion artifacts.
This can be accomplished by the use of sufficiently high tube
current values.
13.Cassettes should be loaded at least 30 minutes in advance to allow
air to escape, and thus improving film/screen contact.
14.The technologist should examine the images after processing in
order to verify that the techniques being used are producing
diagnostic quality images and that the X-ray equipment is
functioning correctly.

15.An appropriate Quality Assurance program must be
implemented on mammographic X-ray equipment and on
film and Xerographic processing systems.

16.While recommended dose limits have been defined for radiation
workers and the general population, there is no specific limits
recommended for patients undergoing diagnostic X-rays
procedures. However, it is possible to provide limits on the
amount of radiation breast tissues receive by setting dose limits
on the level of radiation a representative breast phantom would
receives for a given irradiation. These dose limits are presented
in the following table;

Procedure Mean Glandular Dose Limits
Film-Screen Mammography (no
grid)
1.0 mGy
Film-Screen Mammography (grid
technique)
2.0 mGy
Xeromammography 4.0 mGy
Recommended dose limits per irradiation

Radiological Chest Screening
1. The use of mass radiological screening should only be
considered in areas of high incidence of tuberculosis or in
special population groups who may be particularly susceptible
to lung disease. Selection of population groups for x-ray
screening should be based upon the probability of discovering a
significant number of cases of cardiopulmonary disease and on
the availability of full follow-up facilities for individuals
requiring treatment.
2. Mass x-ray screening of the general population for tuberculosis
and other chest diseases must not be carried out.

Radiological Chest Screening
3. Routine hospital admission chest x-rays should only be taken
in identified high risk groups.
4. Chest x-rays should not be required as a routine part of a pre-
employment medical check-up or for admission to educational
institutions. Since photofluorographic x-ray machines require a
higher level of x-ray exposure than do convential radiographic
machines to produce a film and since the yield of significant
information is low, photofluorographic x-ray machines must
not be used for chest examinations in place of conventional
machines, and should not be used for mass screening when
conventional machines are available.

Guidelines For Carrying Out X-ray
Examinations

1. The operator must not perform any examination which has not
been prescribed by a physician responsible for the patient.
2. The exposure of the patient must be kept to the lowest
practicable value, consistent with clinical objectives and
without loss of essential diagnostic information. To achieve
this, techniques appropriate to the equipment available should
be used.
3. Particular care, consistent with the recommendations of Section
13.2, must be taken when radiological examinations of
pregnant or potentially pregnant women are carried out.

4. The x-ray beam must be well-collimated to restrict it as much
as is practicable to the area of diagnostic interest.
5. The x-ray beam size must be limited to the size of the image
receptor or smaller.
6. The x-ray beam should not be directed towards the gonads
unless it is absolutely essential, in which case gonad
shielding must be used whenever the value of the
examination is not impaired by such use. Guidelines on the
use of gonad shielding are given in section 14 of this
guideline.

7. Shielding should be used where appropriate and practicable to
limit the exposure of body tissues. It is particularly important
that special effort to be made to protect the blood-forming
organs, gonads and thyroids of children.
8. The target-to-skin distance should be as great as possible,
consistent with good radiographic technique.
9. For very young children, special devices should be employed
to restrict movement.
10.Full details of the radiological procedures carried out should be
noted on the patient’s clinical records.

Recommendations For
Radiographic Procedures
1. The edges of the x-ray beam should be seen on all x-ray
films to ensure that no more than the desired area has been
irradiated. The film size used should be as small as possible,
consistent with the diagnostic objectives of the examination.
2. Screen-type film should not be used for non-screen
techniques because it is less sensitive to direct x-radiation
than non-screen film.

Recommendations For
3. The fastest film or intensifying screen-film combination,
consistent with diagnostically-acceptable results, should
be used. When highest definition is not required a high-
speed film-screen combination should be used.

Recommendations For
4. X-ray intensifying screens made from rare earth phosphors
should be used where appropriate. Exposure reductions in
excess of 50%, compared to conventional calcium tungstate
systems, are possible using the rare earth-type intersifying
screens and the films developed for use with such screens.
These reductions result from greater x-ray absorption and
increased conversion efficiencies of the new phosphors —
the rare earth systems have a conversion efficiency of x-rays
to light of 15-20%, compared to approximately 5% for
calcium tungstate systems.

Recommendations For
5. To ensure that patient exposure is kept to a minimum,
consistent with image quality, full advantage should be taken of
a combination of techniques, such as:
a. use of an antiscatter grid or air gap between the patient and the image
receptor;
b. use of the optimum focus-to-film distance appropriate to the
examination;
c. use of the highest kilovoltage which produces films of good quality;
d. use of automatic exposure control devices designed to keep all
exposures and repeat exposures to a minimum.

Recommendations For
6. The radiographer should see the films after processing in
order to verify that the techniques being used are producing
diagnostic quality films and that the x-ray equipment is
functioning correctly.
7. To avoid the necessity of retakes, it is particularly important
before taking a long series of films that a single preliminary
film of the series should be taken and processed to verify
correctness of settings.

Recommendations For
8. While dose limits have been defined for radiation workers and the
general population, no specific limits have been recommended, to
date, for patients undergoing diagnostic x-ray procedures. For
patients the risk involved in the exposure must always be
weighed against the medical requirement for accurate diagnosis.
However, it is now feasible to recommend upper limits on patient
skin entrance exposure, for routine, non-specialty, radiographic
examinations. For a reference patient, having the
anthropometrical characteristics shown in Table 1, the skin
entrance exposure (without backscatter) should not exceed the
values indicated in Table 2.

Recommendations For
Body Part Thickness (cm)
Head (lateral)
Neck (A/P)
Chest (P/A)
Abdomen (A/P)
Foot (D/P)
15
13
23
23
8
Table 1
Anthropometrical Characteristics of the Reference Patient

Recommendations For
Examination (Projection) ESE (mR)
Chest (P/A)
Skull (Lateral)
Abdomen (A/P)
Cervical Spine (A/P)
Thoracic Spine (A/P)
Full Spine (A/P)
Lumbo-Sacral Spine (A/P)
Retrograde Pyelogram (A/P)
Feet (D/P)
20
170
450
120
400
250
500
500
200
Table 2
Recommended Upper Limits on Skin Entrance Exposure

Recommendations For
Fluoroscopic Procedures
1. In view of the relatively high exposure that results from
fluoroscopy, such procedures should only be carried out
when an equivalent result cannot be obtained from
radiography. Fluoroscopy must not be used as a substitute for
radiography.
2. Flurorscopy must only be carried out by, or under immediate
supervision of, a radiologist or physician properly trained in
fluoroscopic procedures.
3. All fluoroscopic procedures should be carried out as rapidly
as possible with the smallest practical x-ray field sizes.

Recommendations For
4. The exposure rate used in fluoroscopy should be as low
as possible and must not exceed 10 roentgens (2.58
mC/kg) per minute at the position where the central axis
of the x-ray beam enters the patient. With modern
equipment, most fluoroscopic procedures can be readily
carried out with exposure rates of less than 5 roentgens
(1.29 mC/kg) per minute.

Recommendations For
5. Image intensification must be used in order to reduce patient
exposure. Image intensifiers can significantly reduce both
exposure rate and exposure time. However, the operator
must monitor the x-ray tube current and voltage on
equipment with automatic brightness control, since both can
rise to high values without the knowledge of the operator,
particularly if the gain of the intensifier is decreased.
6. Television monitoring should be used in conjunction with
the image intensifier.

Recommendations For
7. Mobile fluoroscopic equipment should only be used for
examinations where it is impractical to transfer patients to
a permanent fluoroscopic installation.
8. Cinefluorography produces the highest patient doses in
diagnostic radiology because the x-ray tube currents and
potentials used are generally higher than those used in
fluoroscopy. Therefore, this technique should not be used
unless significant medical benefit is expected.

Recommendations For
Photofluorographic Procedures
1. The x-ray beam must be restricted to the area of the
fluorescent screen and should be limited to the minimum
size consistent with clinical requirements.
2. Appropriate steps must be taken to exclude or shield the
gonads from the direct beam.
3. The performance of the equipment must be monitored
routinely. Special emphasis should be placed on the speed
of the optical systems used. These should be as fast as
possible and should be replaced when noticeable
deterioration in performance occurs.

Procedures
1. Significant exposure to the patient’s eyes can result during
neurological examinations, such as carotid angiography. In
projections where it does not interfere with the diagnostic
information sought, eye shielding should be used.
2. During cardiac catheterization and angiography significant
exposure of the patient’s thyroid gland can occur. Therefore,
appropriate shielding should be used whenever possible

Guidelines For Reduction Of Gonad Dose

Recommendations For Reducing
Gonad Dose To The Patient
Radiologists and radiographers must pay special attention to
four factors that are important for reducing gonad dose to the
patient:
1. Correct collimation of the x-ray beam. — It is not sufficient
merely to limit the beam to the size of the image receptor.
Care should be taken to further restrict the beam to the
region of the patient’s body that is of diagnostic interest.
Irradiation of any part of the body outside that region
contributes nothing to the objective of the examination and
only increases dose both to the body and the gonads.

2. Gonad shielding. — Appropriate use of specific area
gonad shielding is strongly advised when:
(i) the gonads, of necessity, lie within, or are in close
proximity to, the primary x-ray beam;
(ii) the patient has reasonable reproductive potential; and
(iii) clinical objectives will not be compromised.

3. Appropriate selection of technique factors. — An
appropriate selection of tube voltage, current and filtration
is particularly important for diagnostic procedures in
which the gonads lie within or near the primary x-ray
beam. For example, in fluoroscopy, use of higher tube
voltage and filtration and lower tube current will almost
always reduce the gonad dose.

4. Sensitivity of imaging systems. — The gonad dose is
inversely proportional to the sensitivity of the imaging
system. Thus, doubling the sensitivity halves the gonad
dose; conversely, halving the sensitivity doubles the gonad
dose. It is, therefore, very important to maintain the
sensitivity of the imaging system at its optimum value and
to be alert for any significant deterioration.

Recommendations For Reducing Gonad
Dose To Operators
• Adherence to the safe use procedures specified in Section 11 of
this Safety Code will ensure that gonad dose to radiologists and
radiographers is kept to the minimum practicable.

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